Tethyshadros insularis, Dalla Vecchia, 2009

Norman, David B., 2015, On the history, osteology, and systematic position of the Wealden (Hastings group) dinosaur Hypselospinus fittoni (Iguanodontia: Styracosterna), Zoological Journal of the Linnean Society 173 (1), pp. 92-189 : 159-160

TETHYSHADROS INSULARIS DALLA VECCHIA, 2009

Tethyshadros comprises a nearly complete articulat- ed skeleton of a hadrosaur-like (hadrosauromorph – see Systematics section below) iguanodontian collect- ed near Villaggio del Pescatore, Trieste Province, Italy. The specimen was recovered from the Liburnian Formation (Upper Campanian−lower Maastrichtian).

Teeth and jaws

The dentary teeth, although not exposed, are evidently small and lanceolate and bear a single median carina (primary ridge) flanked on either side by a single accessory ridge ( Dalla Vecchia, 2009: fig. 3), and the marginal denticles form simple cones, rather than curved, mammillate ledges. By comparison, the dentary teeth of Hy. fittoni are broad and shield-shaped, have a distally offset primary ridge as well as several additional ridges, and the marginal denticles form ledges that are fringed with irregular mammillae. Tooth replacement patterns, the relative sizes of dentary and maxillary crowns, and the number of teeth in each alveolus and involved in the occlusal surface are all unknown at present. The lower jaw is elongate and slightly arched anteriorly, as is also the case in Hy. fittoni .

Axial skeleton

Most notably, the dorsal vertebrae of T. insularis ( Dalla Vecchia, 2009: fig. 1) bear short, reclined, rectangular neural spines in sharp contrast to the tall, narrow spines seen in Hy. fittoni .

Appendicular skeleton

The pectoral girdle has a hadrosaur-like scapula with a straight acromion that follows the dorsal margin of the blade near its proximal end (unlike the J-shaped form seen in Hy. fittoni ); the sternal plate is hatchetshaped and has a narrow, elongate, rod-like ‘handle’. The forelimb is gracile, with a slender, tapering radius and ulna, a reduced carpus, and slender, elongate metacarpals (this differs markedly from the robust form of these bones in Hy. fittoni ). Digit I of the manus is not present (in striking contrast to Hy. fittoni ). The ilium has a strongly everted dorsal margin in the region posterodorsal to the ischiadic peduncle; this area rather than forming a bevelled thickening is developed into a pendant, tab-like structure referred to as a pendule ( Norman, 2014). The postacetabular process of the ilium forms a flat rectangular plate with the brevis fossa (if present) restricted to its medial surface. The prepubic process is deep, transversely compressed, and expand- ed distally. The ischial shaft is slender, slightly bowed, and tapers distally (there is no terminal boot at the end of the ischial shaft). The femur has a straight shaft. In all these pelvic and hindlimb features this taxon differs markedly from Hy. fittoni .